U.S. patent number 10,481,043 [Application Number 15/702,397] was granted by the patent office on 2019-11-19 for method for small leak testing of an evaporative emissions system.
This patent grant is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS LLC. The grantee listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Todd W Nelson.
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United States Patent |
10,481,043 |
Nelson |
November 19, 2019 |
Method for small leak testing of an evaporative emissions
system
Abstract
A method for small leak testing of an evaporative emissions
system includes monitoring a vacuum pressure level of the
evaporation emissions system with the engine on and actuating a
canister vent valve to regulate the vacuum pressure level to a
predetermined minimum vacuum pressure level. Upon turning the
engine off, the canister vent valve and a canister purge valve are
closed to seal the evaporative emissions system. Next, the vacuum
pressure level is recorded over a predetermined time period after
turning off the engine and a fault code is set when the vacuum
pressure level becomes less than the predetermined minimum vacuum
pressure level.
Inventors: |
Nelson; Todd W (Brighton,
MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC |
Detroit |
MI |
US |
|
|
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS
LLC (Detroit, MI)
|
Family
ID: |
65441758 |
Appl.
No.: |
15/702,397 |
Filed: |
September 12, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190078976 A1 |
Mar 14, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01M
3/3272 (20130101); G01M 15/042 (20130101); G01M
3/26 (20130101); G01M 3/025 (20130101) |
Current International
Class: |
F02M
25/08 (20060101); F02M 33/04 (20060101); G01M
15/04 (20060101); G01M 3/26 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10131162 |
|
Jan 2003 |
|
DE |
|
623736 |
|
Aug 1988 |
|
JP |
|
WO-2013020824 |
|
Feb 2013 |
|
WO |
|
Primary Examiner: Ha; Nguyen Q.
Claims
What is claimed is:
1. A method for small leak testing of an evaporative emissions
system of an engine, the method comprising: monitoring a vacuum
pressure level of the evaporation emissions system with the engine
on; opening a canister purge valve and activating a pump, both of
which are within the evaporative emissions system, to provide a
vacuum pressure level; actuating a canister vent valve within the
evaporative emissions system to regulate the vacuum pressure level
to a predetermined minimum vacuum pressure level; closing the
canister vent valve and the canister purge valve when the engine is
turned off; deactivating the pump; recording the vacuum pressure
level over a predetermined time period after the engine is turned
off and the pump is deactivated; and setting a fault code when the
vacuum pressure level becomes less than the predetermined minimum
vacuum pressure level.
2. The method of claim 1 wherein monitoring further comprises
monitoring the vacuum pressure level at a fuel tank within the
evaporative emissions system using a pressure sensor.
3. The method of claim 1 wherein monitoring further comprises
monitoring the vacuum pressure level at an evaporative emissions
vapor canister within the evaporative emissions system using a
pressure sensor.
4. The method of claim 1 wherein actuating further comprises
opening and closing the canister vent valve with a variable pulse
width modulated signal to regulate the vacuum pressure level.
5. The method of claim 1 wherein actuating further comprises
actuating the canister vent valve between a fully open and a fully
closed position to regulate the vacuum pressure level.
6. The method of claim 1 further comprises controlling duty cycle
of a signal applied to the canister purge valve to regulate the
vacuum pressure level when the canister vent valve is
restricted.
7. The method of claim 1 wherein actuating further comprises
actuating a purge pump to affect regulation of the vacuum pressure
level.
8. The method of claim 1 wherein setting further comprises
activating a malfunction indicator lamp when the vacuum pressure
level becomes less than the predetermined minimum vacuum pressure
level.
9. A method for small leak testing of an evaporative emissions
system of an engine, the method comprising: monitoring a vacuum
pressure level of the evaporation emissions system with the engine
on; opening a canister purge valve and activating a pump, both of
which are within the evaporative emissions system, to provide the
vacuum pressure level; actuating a canister vent valve within the
evaporative emissions system with a variable pulse width modulated
signal to regulate the vacuum pressure level to a predetermined
minimum vacuum pressure level; closing the canister vent valve and
the canister purge valve when the engine is turned off;
deactivating the pump; recording the vacuum pressure level over a
predetermined time period after the engine is turned off and the
pump is deactivated; and setting a fault code when the vacuum
pressure level becomes less than the predetermined minimum vacuum
pressure level.
10. The method of claim 9 wherein monitoring further comprises
monitoring the vacuum pressure level at a fuel tank within the
evaporative emissions system using a pressure sensor.
11. The method of claim 9 wherein monitoring further comprises
monitoring the vacuum pressure level at an evaporative emissions
vapor canister within the evaporative emissions system using a
pressure sensor.
12. The method of claim 9 wherein actuating further comprises
actuating the canister vent valve between a fully open and a fully
closed position to regulate the vacuum pressure level.
13. The method of claim 9 further comprises controlling duty cycle
of a signal applied to the canister purge valve to regulate the
vacuum pressure level when the canister vent valve is
restricted.
14. The method of claim 9 wherein actuating further comprises
actuating a purge pump to affect regulation of the vacuum pressure
level.
15. The method of claim 9 wherein setting further comprises
activating a malfunction indicator lamp when the vacuum pressure
level becomes less than the predetermined minimum vacuum pressure
level.
Description
FIELD
The present disclosure relates to an evaporative emissions system
and more particularly to a method for small leak testing of an
evaporative emissions system.
BACKGROUND
This section provides background information related to the present
disclosure which is not necessarily prior art.
Internal combustion engines combust a mixture of air and fuel to
generate torque. The fuel may be a combination of liquid fuel and
vapor fuel. A fuel system supplies liquid fuel and vapor fuel to
the engine. A fuel injector provides the engine with liquid fuel
drawn from a fuel tank. An evaporative emissions system, typically
including, but not limited to, a fuel tank, a vapor canister, a
vent valve, a purge valve, and maybe a purge pump, provides the
engine with fuel vapor drawn from the fuel tank and vapor
canister.
The liquid fuel stored within the fuel tank may vaporize and form
fuel vapor. The vapor canister traps and stores the fuel vapor to
prevent it from escaping into the atmosphere from the system. It is
known that fuel vapor may sometimes escape into the atmosphere
through small leaks in the system, e.g., at the gas cap or other
means, that can contribute to air pollution.
Some system tests for fuel vapor leaks rely on heat generated from
the engine to produce changes in pressure when the system is
closed. However, future fuel efficient engines that produce a low
heat signature, may not provide the heat necessary to generate
enough pressure for running a leak test. It is desirable to have a
fuel vapor leak test suitable for future fuel efficient vehicles
having low heat signature engines.
SUMMARY
This section provides a general summary of the disclosure, and is
not a comprehensive disclosure of its full scope or all of its
features.
In accordance with an exemplary embodiment, a method for small leak
testing of an evaporative emissions system includes monitoring a
vacuum pressure level of the evaporation emissions system with
engine on. Another aspect includes actuating a canister vent valve
to regulate the vacuum pressure level to a predetermined minimum
vacuum pressure level. And another aspect includes closing the
canister vent valve and a canister purge valve when the engine is
turned off. Still another aspect includes recording the vacuum
pressure level over a predetermined time period after turning off
the engine. And still another aspect includes setting a fault code
when the vacuum pressure level becomes less than the predetermined
minimum vacuum pressure level.
Further aspects in accordance with the exemplary embodiment wherein
monitoring further includes monitoring the vacuum pressure level at
a fuel tank or at the evaporative emissions vapor canister within
the evaporative emissions system using a pressure sensor. And a
further aspect wherein actuating further includes opening and
closing the canister vent valve with a variable pulse width
modulated signal to regulate the vacuum pressure level. Yet another
aspect wherein actuating further includes actuating the canister
vent valve between a fully open and a fully closed position to
regulate the vacuum pressure level. Still another aspect includes
controlling duty cycle of a signal applied to the canister purge
valve to regulate the vacuum pressure level when the canister vent
valve is restricted. And still another aspect wherein actuating
further comprises actuating a purge pump to affect regulation of
the vacuum pressure level. And one other aspect wherein setting
further comprises activating a malfunction indicator lamp when the
vacuum pressure level becomes less than the predetermined minimum
vacuum pressure level.
Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
DRAWINGS
The drawings described herein are for illustrative purposes only of
selected embodiments and not all possible implementations, and are
not intended to limit the scope of the present disclosure.
FIG. 1 is a functional block diagram of an example direct injection
engine system in accordance with an exemplary embodiment;
FIG. 2 illustrates an example fuel system and control system in
accordance with the exemplary embodiment; and
FIG. 3 is an algorithm of a method for small leak testing of an
evaporative emissions system in accordance with the exemplary
embodiment.
Corresponding reference numerals indicate corresponding parts
throughout the several views of the drawings.
DETAILED DESCRIPTION
Example embodiments will now be described more fully with reference
to the accompanying drawings.
Example embodiments are provided so that this disclosure will be
thorough, and will fully convey the scope to those who are skilled
in the art. Numerous specific details are set forth such as
examples of specific components, devices, and methods, to provide a
thorough understanding of embodiments of the present disclosure. It
will be apparent to those skilled in the art that specific details
need not be employed, that example embodiments may be embodied in
many different forms and that neither should be construed to limit
the scope of the disclosure. In some example embodiments,
well-known processes, well-known device structures, and well-known
technologies are not described in detail.
The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a," "an," and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. The
method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the
particular order discussed or illustrated, unless specifically
identified as an order of performance. It is also to be understood
that additional or alternative steps may be employed.
When an element or layer is referred to as being "on," "engaged
to," "connected to," or "coupled to" another element or layer, it
may be directly on, engaged, connected or coupled to the other
element or layer, or intervening elements or layers may be present.
In contrast, when an element is referred to as being "directly on,"
"directly engaged to," "directly connected to," or "directly
coupled to" another element or layer, there may be no intervening
elements or layers present. Other words used to describe the
relationship between elements should be interpreted in a like
fashion (e.g., "between" versus "directly between," "adjacent"
versus "directly adjacent," etc.). As used herein, the term
"and/or" includes any and all combinations of one or more of the
associated listed items.
Although the terms first, second, third, etc. may be used herein to
describe various elements, components, regions, layers and/or
sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the example embodiments.
An evaporative emissions system includes a fuel tank and a vapor
canister that traps and stores fuel vapor produced from liquid fuel
in the fuel tank. A canister purge valve is selectively opened to
purge the fuel vapor from the vapor canister to an internal
combustion engine. In some types of engines, such as naturally
aspirated engines, vacuum within an intake manifold may be used to
draw fuel vapor through the canister purge valve. Other types of
engines, such as boosted engines, may have insufficient vacuum or
boost to draw fuel vapor through the canister purge valve. A pump
may be used to pump fuel vapor from the vapor canister to an intake
system of engines having insufficient boost or vacuum. Some
canister purge valves may be directly coupled to a component of an
intake system of an engine.
A control module selectively opens the canister purge valve (which
is normally closed) and activates a pump after closing a canister
vent valve to provide a vacuum in the evaporative canister
emissions system for determining whether there is a leak in the
system. The leak could be due to the purge valve being detached
from an intake system of an engine, or due to holes in the
evaporative canister emissions system.
Closing the canister purge valve prevents fuel vapor flow into the
intake system. However, fuel vapor may exit the canister purge
valve when the canister purge valve is detached from the intake
system. The control module therefore determines whether the
canister purge valve is detached based on whether a pressure
measured at a location between the fuel tank and the canister purge
valve decreases over time when the canister purge valve is closed
and the canister vent valve is also closed.
Referring now to FIG. 1, a functional block diagram of an example
engine system for a vehicle is presented. An engine 10 combusts an
air/fuel mixture to produce drive torque for a vehicle. While the
engine 10 will be discussed as a spark ignition direct injection
(SIDI) engine, the engine 10 may include another type of engine.
One or more electric motors and/or motor generator units (MGUs) may
be provided with the engine 10.
Air flows into the engine 10 via an intake system 12. More
specifically, air flows into an intake manifold 14 through a
throttle valve 16. The throttle valve 16 may vary airflow into the
intake manifold 14. A throttle actuator module 18 (e.g., an
electronic throttle controller or ETC) controls opening of the
throttle valve 16 based on signals from an engine control module
(ECM) 20. In various implementations, the intake system 12 includes
one or more boost devices, such as one or more superchargers and/or
one or more turbochargers that increase airflow into the intake
manifold 14 and, therefore, the engine 10.
Air from the intake manifold 14 is drawn into cylinders of the
engine 10. While the engine 10 may include more than one cylinder,
only a single representative cylinder 22 is shown. Air from the
intake manifold 14 is drawn into the cylinder 22 through one or
more intake valves of the cylinder 22, such as an intake valve 24.
One or more intake valves 24 may be provided with each cylinder
22.
A fuel actuator module 26 controls fuel injectors of the engine 10,
such as fuel injector 28, based on signals from the ECM 20. A fuel
injector 28 may be provided for each cylinder. The fuel injectors
28 inject fuel, such as gasoline, for combustion within the
cylinders. The ECM 20 may control fuel injection to achieve a
target air/fuel ratio, such as a stoichiometric air/fuel ratio.
The injected fuel mixes with air and creates an air/fuel mixture in
the cylinder 22. Based upon a signal from the ECM 20, a spark
actuator module 30 may energize a spark plug 32 in the cylinder 22.
A spark plug 32 may be provided for each cylinder. Some types of
engines, such as diesel engines, do not include spark plugs. Spark
generated by the spark plug 32 ignites the air/fuel mixture.
Exhaust resulting from combustion is expelled from the cylinder 22
via one or more exhaust valves, such as exhaust valve 34, to an
exhaust system 36. One or more exhaust valves may be provided for
each cylinder.
Referring now to FIG. 2, a functional block diagram of an example
fuel system 40 is presented. The fuel system 40 supplies fuel to
the engine 10. More specifically, the fuel system 40 supplies both
liquid fuel and fuel vapor to the engine 10. The fuel system 40
includes a fuel tank 42 that contains liquid fuel. Liquid fuel is
drawn from the fuel tank 42 and supplied to the fuel injectors of
the engine 10 by one or more fuel pumps (not shown).
Some conditions, such as refueling, heat, vibration, and/or
radiation, may cause liquid fuel within the fuel tank 42 to
vaporize. A vapor canister 44 traps and stores vaporized fuel (fuel
vapor). The vapor canister 44 may include one or more substances
that trap and store fuel vapor, such as a charcoal.
A canister purge valve 46 includes a valve member that is
selectively opened and closed to enable and disable, respectively,
fuel vapor flow to the engine 10. In accordance with the exemplary
embodiment, the canister purge valve 46 is normally closed.
Operation of the engine 10 may create a vacuum relative to ambient
pressure within the intake manifold 14.
In some instances, such as when one or more boost devices are
increasing airflow into the engine 10, pressure within the intake
manifold 14 may be greater than or approximately equal to ambient
pressure. A pump 48 may be implemented that pumps fuel vapor from
the vapor canister 44 to the canister purge valve 46. When the
canister purge valve 46 is open, the pump 48 also pumps fuel vapor
from the vapor canister 44 toward the engine 10.
The ECM 20 controls the canister purge valve 46 and the pump 48 to
control the flow of fuel vapor to the engine 10. The ECM 20 may
also control a canister vent valve 50. When the canister vent valve
50 is in a closed position, the ECM 20 may selectively open the
canister purge valve 46 and turn on the pump 48 connected to the
canister purge valve 46 to purge fuel vapor from the vapor canister
44 to the intake system 12, thereby providing a vacuum pressure
level in the evaporative emissions system.
In accordance with the exemplary embodiment, when the engine is on,
the ECM 20 operates to monitor and regulate the vacuum pressure
level in the evaporative emissions system to a predetermined
minimum vacuum pressure level by controlling opening and closing
the canister vent valve 50 with a variable pulse width modulated
signal.
A pressure sensor 47 measures a vacuum pressure level at a location
between the pump 48 and the canister purge valve 46 and is in
communication with the ECM 20. The pressure sensor 47 may be
disposed at the fuel tank or at the vapor canister to operate
within the scope of the exemplary embodiment for monitoring the
vacuum pressure level within the evaporative emissions system.
When the engine is turned off, the ECM 20 closes the canister vent
valve 50 and a canister purge valve 46 and begins recording the
vacuum pressure level over a predetermined time period, e.g., 1 to
3 minutes, after turning off the engine. If the vacuum pressure
level is determined to become less than the predetermined minimum
vacuum pressure level then a fault code is set in the ECM and a
malfunction indicator lamp (MIL) will illuminate with ignition
on.
Alternately, the ECM 20 may also control the rate at which fuel
vapor is purged (a purge rate) by controlling opening and closing
of the canister purge valve 46. For example only, the ECM 20 may
control the canister purge rate by controlling a variable duty
cycle of a signal applied to the canister purge valve 46. Ambient
air flows into the vapor canister 44 as fuel vapor flows from the
vapor canister 44 toward the intake system 12. As the canister vent
valve 50 modulates to create vacuum in the tank, the canister purge
valve 46 may operate as a higher duty cycle to maintain the desired
flow rate.
Liquid fuel may be added to the fuel tank 42 via a fuel inlet 52. A
fuel cap 54 seals the fuel inlet 52. The fuel cap 54 and the fuel
inlet 52 may be accessed via a fueling compartment 56. A fuel door
58 may be implemented to shield and close the fueling compartment
56.
The ambient air provided to the vapor canister 44 through the
canister vent valve 50 may be drawn from the fueling compartment
56. A filter 60 receives the ambient air and filters various
particulate from the ambient air. The canister vent valve 50 may be
actuated to the open canister vent position or the closed position.
The canister vent valve 50 is shown as being in the canister vent
position in the example of FIG. 2. When the canister vent valve 50
is in the canister vent position, air can flow from the filter 60
to the vapor canister 44 via a first path 62 through the canister
vent valve 50. When the canister vent valve 50 is in the closed
position, air can flow between a vacuum pump 64 and the vapor
canister 44 via a second path 66 through the canister vent valve
50.
The canister purge valve 46 is directly coupled to a component of
the intake system 12, such as the intake manifold 14 or an intake
pipe through which air flows into the intake manifold 14. In
engines having a boost device, the canister purge valve 46 may be
directly coupled to a component upstream of the boost device.
FIG. 3 is an algorithm 100 of a method for small leak testing of an
evaporative emissions system in accordance with the exemplary
embodiment. The method begins at block 102 with monitoring a vacuum
pressure level of the evaporation emissions system with engine on.
In conventional evaporative testing methodology, the pressure
levels are monitored during engine off and after the pressure is
purged before closing the system valves to allow pressure to
generate due to heat from the engine emissions system. This heat
generated pressure is then used to facilitate the leak testing. In
accordance with aspects of the exemplary embodiment, this heat
generated pressure is not required as it may not be available in
more efficient engines.
At block 104, the method continues with actuating a canister vent
valve to regulate the vacuum pressure level to a predetermined
minimum vacuum pressure level. Actuating includes opening and
closing the canister vent valve with a variable pulse width
modulated signal to regulate the vacuum pressure level to a
predetermined minimum level when the engine is on. In this manner,
generation of heat to build pressure to facilitate the testing
after the engine is turned off is not required. The method may also
include actuating the canister vent valve between a fully open and
a fully closed position to regulate the vacuum pressure level but
this approach is less refined than using the pulse width modulation
control actuation described above.
Alternatively, the vacuum pressure level may be regulated by
controlling the duty cycle of a signal applied to the canister
purge valve 46 when the canister vent valve 50 is restricted (i.e.,
in the closed position). It is appreciated that the results
regarding regulation of the vacuum pressure level within the
evaporative emissions system will be substantially equivalent to
the actuation of the canister vent valve 50 approach using a
variable duty cycle.
At block 106, the method continues with closing the canister vent
valve and a canister purge valve when the engine is turned off to
seal the system before starting the leak testing. At this point, no
additional pressure is required to be added to the system because
the method is operative to maintain a predetermined minimum vacuum
pressure throughout the engine on/off process in accordance with
aspects of the exemplary embodiment.
Next, at block 108, the method continues with recording the vacuum
pressure level over a predetermined time period after turning off
the engine. The recording is performed by the ECM that is in data
communication with a pressure sensor disposed within the
evaporative emissions system between the fuel tank and the canister
purge valve. The predetermined time period for running the leak
test and recording the results in accordance with the exemplary
embodiment provides an energy efficiency advantage over the
conventional leak testing methods as the disclosed method requires
less time and energy to obtain results.
At block 110, the method continues with determining if the vacuum
pressure level is/becomes less than the predetermined minimum level
within the predetermined time period. If so, then at block 114, the
method continues with setting a fault code or MIL when the vacuum
pressure level becomes less than the predetermined minimum vacuum
pressure level. The fault code and MIL will remain set until the
engine is serviced. If the vacuum pressure is determined not to be
less than the predetermined minimum vacuum pressure then, at block
112, the method determines if the predetermined time period for
testing is expired. If so the method ends, but if not, then the
method returns to block 108.
The foregoing description of the embodiments has been provided for
purposes of illustration and description. It is not intended to be
exhaustive or to limit the disclosure. Individual elements or
features of a particular embodiment are generally not limited to
that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the disclosure, and all such modifications are intended to be
included within the scope of the disclosure.
* * * * *